Tom Karwin: Bees are essential &mdash; and dying off

The puzzle of recent years — what's killing the bees? — appears to be close to solution.

Scientists have said that the cause of the bees' mysterious Colony Collapse Disorder (CCD) could be a combination of factors. The possible explanations always include uses of pesticides that have beneficial effects in agriculture, but that are toxic to bumblebees and honeybees.

Both kinds of bees are essential to the success of about one-third of U.S. food crops. As the bees die, our food supply is subject to very serious threat.

Increasingly, the focus is on neonicotinoids, a class of chemicals that are used as systemic insecticides in commercial agriculture and residential gardening.

This year, an estimated 500,000 bees were found dead or dying in Oregon. Ironically, this largest-known incident of bumblebee deaths occurred during National Pollinator Week, an annual celebration of the valuable ecosystem services provided by bees, birds, butterflies, bats and beetles.

The Oregon Department of Agriculture soon confirmed a neonicotinoid insecticide, dinoterfuran, caused the bee die-off and announced a temporary ban on its applications on landscape trees and shrubs, nursery and greenhouse plants, turf grass, forests and agricultural crops."

Despite growing evidence of the negative impact of these pesticides on bee populations, and the European Commission's continentwide suspension of neonicotinoids, the U.S. Environmental Protection Agency has been looking for other explanations of CCD and has established a 2018 deadline for completing its reviews of the major neonicotinoids.

Earlier this year, commercial beekeepers and environmental groups petitioned the EPA to suspend uses of the pesticides, and, in early July, a coalition of environmental groups urged President Obama to direct the EPA to follow the European Commission's lead by suspending use of neonicotinoids.

This is high drama, with great consequences for our food supply and our gardens. There are several sides to significant issues, and this one is no different.

Restricting applications of widely used synthetic chemical pesticides will impact farmers' practices and constrict the revenue streams for manufacturers of agricultural chemicals. It will be interesting to see what arguments they will devise to justify the systematic killing of a critically important group of farmworkers: the honeybees.

· Download and read "Help the Honeybees: A List of Pesticides to Avoid" (centerforfoodsafety.org/ fact-sheets). This is another free publication with a surprising list of popular pesticides that contain neonicotinoids.

· Take the Pesticide-Free Zone Pledge and post a Pesticide-Free Zone sign in your garden (beyondpesticides.org/ pesticidefreelawns/ pfzsign/). Bees and other beneficial insects will thank you!

Tom Karwin is a Santa Cruz resident, a UC master gardener, a member of several garden groups, and vice president of the UCSC Arboretum Associates. Contact him at gardening@karwin.com.